I've read online that the size of the vortex in a yeast starter does not matter. Why is this true?

When I was experimenting with water yesterday, I created a monster vortex (very cool) and could see air bubbles screaming all over the water; turning the vortex down into a baby vortex resulted in no air bubbles screaming all over. Some people say that the point of the vortex is just to keep the yeast in suspension which will make contact with the air in the vortex. Others say you need a monster vortex so that the air bubbles can scream through the solvent and aerate the wort. Which is correct?

If you simply stir your 5 gallons of wort, it will not aerate much at all. The reason you splash it is to introduce oxygen bubbles into the wort, which aerates it better. Given that everyone agrees on this, why would a small vortex with no screaming air bubbles be able to aerate the yeast starter?

EDIT: Well I figured if the point of the vortex was to aerate the yeast-starter, why not use my aeration-stone and oxygen tank? So I hung the stone in for 60 seconds which created a lot of foam, but the stir plate got rid of the foam.

It made me think: now that my yeast starter is aerated, why should I care about the size of the vortex (given the assumption that the greater the vortex, the greater the aeration)?

Why care about the vortex at all (given the assumption that vortex size has nothing to do with aeration) ?

  • 3
    No answer, I just like the idea of "screaming air bubbles".
    – object88
    Commented Jun 9, 2013 at 21:30
  • Not an answer, just a guess: wort has a oxygen saturation point, after which no more oxygen can go into solution. It could be that the saturation point is reached quickly with even a small vortex, so a large one is unnecessary. Commented Jun 9, 2013 at 22:17
  • Commenting on the EDIT. The yeast consume oxygen to reproduce. That's the reason for the constant aeration provided by the vortex. You can saturate the wort with oxygen at the beginning, but unless you continually add oxygen throughout fermentation, you'll get fewer cells because that initial does of oxygen has been consumed. Commented Jun 9, 2013 at 22:57

1 Answer 1


http://braukaiser.com/blog/blog/2013/03/25/stir-speed-and-yeast-growth/ and the first link it contains address these points exactly.

  • 4
    could you paraphrase the results here?
    – mdma
    Commented Jun 10, 2013 at 2:15
  • Also interesting points to consider are: 1. the distribution of nutrients in the wort, 2. the possible issues of flocculation on starting a bigger culture and how the speed of the vortex disrupts this, and 3. level of stress the yeast encounter and how a stronger vortex improves the environment making the yeasties happier. I bet that all of these are impacted by the vortexing and may combined with oxygen levels lead to a better starter. Commented Jun 10, 2013 at 16:48

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